1. Field of the Invention
The present invention relates to an image display apparatus for displaying an image and a control method of the image display apparatus and, in particular, to a technique for extracting and displaying an area from an image.
2. Description of the Related Art
Techniques for extracting an area from an input image and displaying the area on a display screen have been put into practical use. Japanese Patent Laid-Open No. 05-337077 proposes such a display apparatus.
A problem with the technique disclosed in Japanese Patent Laid-Open No. 05-337077 will be described below. The technique disclosed in Japanese Patent Laid-Open No. 05-337077 extracts and enlarges a desired area from an input original image and displays the area as a main window. A sub-window displaying the original image is displayed in a portion of the main window so that the original image (sub-window) is superimposed on the image extracted and enlarged from the original image. The technique in Japanese Patent Laid-Open No. 05-337077 displays the sub-window all the time while the area extracted and enlarged from the input original image is displayed as the main window, regardless of whatever is contained in the main window. This is because the sub-window displaying the original image is superimposed on the image of the extracted area in order to enable an operator to readily identify which portion of the original image corresponds to the area extracted and enlarged from the original image. Accordingly, even when the enlarged image displayed in the main window is of interest to the operator and the operator can perform manipulations on the display of the main window alone without any difficulty, a portion of the main window is always occupied by the sub-window displaying the original image. Therefore, there is a problem that the overall main window enlarged cannot completely be viewed because the sub-window interferes with viewing of the image in the main window.